Tests Flashcards
Test for oxygen
A glowing splint relighting
Test for carbon dioxide
Limewater goes milky
Why does limewater go milky when you add carbon dioxide?
Carbon dioxide reacts with the calcium hydroxide forming calcium carbonate and water
Test for chlorine
Will bleach damp litmus paper,
What happens when you test for chlorine with blue litmus paper?
Blue litmus paper will turn red first then white - acidic gas
Test for ammonia
Turns damp red litmus paper blue (alkali)
Test for water
White anhydrous copper (II) sulphate turns blue
What type of reaction is the chemical test for water
Reversible, very exothermic
What is the physical test for water?
Boils at 100 degrees Celsius
Test for positive ions (cations)
Flame test
Describe a flame test
- Clean a piece of nichrome wire by dipping it in hydrochloride acid
- When the wire no longer gives a colour when placed in a roaring flame
- It is then dipped into what you are testing
- Observe colour
What colour do calcium ions go in a flame test
Brick red
What colour do potassium ions go in a flame test?
Lilac
What colour do sodium ions go in a flame test
Orange-yellow
What colour do lithium ions go in a flame test?
Red (Crimson)
What is the test for hydroxide ions?
- Add sodium hydroxide solution
2. Observe colour of precipitate
Why does the hydroxide test work?
Because most metal hydroxides are insoluble in water (except group 1 metals)
What colour does copper (II) precipitate form
Blue
What colour does iron (III) precipitate form
Orange-brown
What colour does iron (II) precipitate form
Green
Test for carbonate ions (CO32-)
- Add dilute nitric acid
- Bubbles of gas will be observed
- Gas can be tested with limewater (carbon dioxide)
Test for sulphate ions (SO42-)
- Add dilute hydrochloric acid
- Add barium chloride
- If sulphate ions are present a white precipitate is formed (barium sulphate)
Why does the test for sulphate ions work?
Because barium sulphate is insoluble
Formula for barium sulphate
BaSO4 (white precipitate)
Test for halides
- Add dilute nitric acid
- Add silver nitrate solution
- Observe colour of precipitate
What colour do chloride ions go in the halide test
White
What colour do bromide ions go in the halide test
Cream
What colour do iodide ions go in the halide test
Yellow
Test for hydrogen
Lit splint goes out with squeaky pop